Problem: $\dfrac{8}{10} + \dfrac{20}{100} = {?}$
Answer: The fractions must have the same denominator before you can add them. Rewrite $\dfrac{8}{10}$ as $\dfrac{80}{100}$ $\dfrac{80}{100} + \dfrac{20}{100} = {?}$ $ = \dfrac{100}{100}$